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Diesel Engines Running Backwards
The only story I can come close to in this group starts out “One day as the old ship was pulling into Naples … .”
https://en.wikipedia.org/wiki/USS_Shasta_(AE-6)
The USS Shasta (AE-6) was built about 1940 intended to be a banana boat (really) but was taken by the Navy and turned into an ammunition ship. She was a diesel ship (a Motor Vessel) with two 9-cyinder Nordberg engines rated at about 3100 HP at 225 RPM. (See the attached picture). (The bottom of the engine foundation was on the keel, there was a platform deck about halfway up the engines and the top of the engine was on another deck about waist high.) These engines would idle at about 45 rpm and you could see every head jump as the cylinder fired. The engines were geared through a set of reduction gears and clutches to a single shaft.
Since we did not have a reverse turbine like steam driven ships, it would take a while to execute a change from “All Ahead Slow” to “Back One-Third”. Now, I was an electronics twidget, but I still crawled in the engine room since I had some depth finder stuff poking through the bottom down there. I learned a bit about the propulsion plant.
If we were entering port where maneuvering might be needed, the engine room had a protocol they followed. If an “All Stop” was given, it might be in preparation for a ”Back One-Third”. In this case, one engine was left at idle and disengaged from the reduction gear and the other engine would be shut down awaiting the next command. To reverse one of these engines, somewhere in the timing system an air driven cam had to be rotated to alter when things happened. Since it took time to stop, swing the cam and restart the engine that is why one engine was shut down; the other engine could handle slow speed “Ahead” maneuvers.
BUT, most good stories start that way, one day as were heading into Naples the harbor pilot we had on board did not appreciate the delicacy of handling 12,000 gross tons of ship and high explosives, the slow engine room response of a Motor Vessel and just what would happen when a gust of wind hit the sail area of the hull and superstructure. Things got out of hand and the Pilot’s engine commands went from “All Ahead Slow” to “Back One-Third” with no “All Stop” to get ready.
The port engine was disengaged and dumped to idle, the starboard engine was disengaged and the “Back One-Third” command was acknowledged, but in an effort to react to the engine commands “smartly” (that’s Navy for dang fast before we hit something), whoever was on the high pressure air start manifold hit the start air before the engine had come to a stop from running “Ahead”.
Things got really busy all over the engine room. When the high pressure air hit the top of the cylinder(s) coming up to compression, relief valves opened all over the place. There was smoke, dust, dirt, rust, scale and exhaust everywhere. To those of us elsewhere in the ship – it felt like an explosion and nothing bothers an ammunition ship sailor more than an explosion. Most of us were at General Quarters before the alarm even sounded and the smoke and stuff coming out of the engine room ventilators didn’t make us feel very good.
But, things did settle down quickly. No fire, the other engine went to “Back One-Third”, we didn’t hit anyone. The only material damage was a pipe plug that blew out of a high pressure air line, sailed past an Engineman’s head and went through two metal lockers like an artillery shell.
The engineers did some teardown to inspect things, no damage to that big Nordberg. It took several days in port to clean up all the dust, dirt and soot in the engine room, the laundry did extra loads of underwear and the Engineering Officer of the Watch and the Throttle man got some extra instruction in how to do things.
But, after all these years as I tell this story – I just had a thought cross what is left of my mind. About six months later that engine developed a crack in the bull gear that drove the induction blowers. The engine was shutdown and we limped home from Turkey to Norfolk at 8-knots. It was an engineering casualty that eventually led to the end of Shasta’s service – she was just too old to fix. I wonder if that abrupt stop may have started a fatigue crack?
